This invention relates to microwave radios, and, more particularly, to a radio frequency unit for a microwave radio.
Microwave radio communications are widely used to transfer large amounts of data, such as in earth and space microwave long-distance communications links. They are also of interest for shorter-range, lower-power applications such as the basic voice, video, and data links between, for example, a cellular base station and the central telephone office. In such applications, the microwave transmission distance is typically between about 0.5-5 miles, the microwave signal may be a specific frequency between about 2-94 GHz, and the power output of the microwave transmitter is about 100 milliwatts. Such microwave communications system are generally termed xe2x80x9cpoint-to-pointxe2x80x9d systems.
Corresponding to the high-power microwave communications systems, a conventional point-to-point system has three basic physical parts: a signal processing unit (SPU), sometimes termed an xe2x80x9cindoorxe2x80x9d unit having the baseband radio components, a radio frequency (RF) unit (RFU), sometimes termed an xe2x80x9coutdoorxe2x80x9d unit having the microwave frequency radio components, and an antenna. Because a microwave feed is required between the components operating at microwave frequency, the radio frequency unit is located within a few feet of the antenna, which ordinarily is mounted outside and aimed at another point-to-point terminal located some distance away. The antenna is typically a parabolic antenna of the cassegrain type. The signal processing unit may be located quite some distance from the radio frequency unit. An ordinary cable set extends between the signal processing unit and the radio frequency unit, but a microwave coaxial feed is required between the radio frequency unit and the antenna.
As point-to-point systems become more popular, their physical packaging becomes more important. The existing radio frequency units and antennas are bulky and, in many cases, difficult to mount, align, and maintain in alignment. With the proliferation of point-to-point systems in large cities, new mounting space on existing masts and elsewhere has become more difficult to find. Installers must hoist the subsequently installed radio frequency unit and antenna to ever-more-precarious locations in order to establish line-of-sight contact with the remote terminal. Conventional point-to-point radio frequency units and antennas may be obtrusive and unsightly, particularly when large numbers of them are concentrated in the available space.
There is a need for an improved radio frequency unit and antenna which overcomes these problems. The present invention fulfills this need, and further provides related advantages.
The present invention provides an integrated point-to-point microwave radio frequency unit/antenna. The integrated radio frequency unit/antenna is compact and lighter than existing units, easily handled and mounted, and readily aligned and maintained in alignment. It can be mounted in locations which would not be practical for conventional microwave radio frequency units and antennas, such as windows of office buildings. The installer need be concerned with only a single box, not two separate components with a microwave cable extending between them, as is the case for some existing systems. The flat-plate, integrated radio frequency unit/antenna is consequently much less visually obtrusive than conventional systems using a parabolic dish antenna.
In accordance with the invention, an integrated point-to-point microwave radio frequency unit/antenna comprises a housing having an exterior wall, a microwave radio frequency transceiver electronics package within the housing and having an antenna connection, a flat antenna integral with the exterior wall of the housing, and a microwave radio frequency feed communicating between the flat antenna and the antenna connection of the microwave transceiver electronics package. There is desirably a means such as a bracket structure built into another wall of the housing to affix the housing to a support structure.
The flat antenna is preferably a continuous transverse stub antenna that is rectangular in shape and relatively thin. It may built into the side of the housing as part of the wall, or more preferably, built as a separate unit and attached integrally to the wall of the housing. The required size of the antenna is dependent upon the frequency at which it is used. For example, such a flat antenna with 38 dB of gain when used for transceiving at 38 GHz is typically 10-xc2xd inches by 10-xc2xd inches in transverse extent, the square antenna being a special case of the rectangular antenna, and about 1 inch thick. The housing, including all of the electronics package, is typically about 12 inches by 12 inches in transverse dimensions, and about 3 inches thick. The entire radio frequency unit/antenna is thus no larger than a small cosmetics case. It is easily handled, mounted, and aimed. By contrast, a conventional radio frequency unit itself has a size of about 12 inches by 12 inches by 12 inches, and the associated parabolic antenna has a diameter of 12-24 inches.
The approach of the invention also offers electronic features not possible with a conventional approach. The microwave feed between the electronics package and the antenna is on the order of at most a few inches and is inside the housing, reducing the possibility of damage or interference. The preferred continuous transverse stub flat antenna may be electronically aimed to achieve fine adjustment of the alignment and to maintain alignment when mounting conditions change, such as when a mounting mast sways or a building deforms due to thermal effects during the course of a day.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.